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Exoplanets - Planets Beyond Our Solar System


Waspie_Dwarf

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I tried to come up with a "your planet is so fat" joke, but I drew a blank. It's late...

Past a certain point I can't even fathom super dense material like that...feathers-got it...bricks-got it...lead-got it... size 8 density in a size 1 planet (that I haven't been too), I don't have that one...

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your planet is so fat it has an oval shaped orbit! :D .....B

your welcome!

Edited by Barek Halfhand
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Three points:

1 I don't like the name of this planet, it makes it sounds just like a number :(

2 It sounds like it would take a fair time to sail around the world on that planet.

3 With an orbit like that, it sounds drunk!

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1 I don't like the name of this planet, it makes it sounds just like a number :(

It is just a number in the scheme of things. Just one planet among (almost certainly) billions.

With so many new exoplanets being found (there are now more than 200 of them and more are being discovered every week) giving them all nice name is simply not possible. Hence the planets are known either by the survey that discovered them (this planet was discovered by the HATnet survey hence the name). They are also known by the same name as there parent star with a lower case letter (starting from b ) as a suffix to show the order that the planets around that star were discovered in. Hence the official name for this planet is actually: HD 147506 b

2 It sounds like it would take a fair time to sail around the world on that planet.

It would be difficult. A planet this size is likely to give off a considerable amount of internal heat. This combinded with the fact that it is so close to its parent star means it will be a very hot world. It is also a gas giant so it will not have a surface like the Earth. It will essentially consist of an atmosphere which gets gradually denser as you go deeper. This atmosphere eventually becomes a liquid and then a solid, but the pressure would be so great that you would be crushed long before you reached the liquid.

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Several Jupiter sized planets found to have only weak Earth like gravity


The University of Warwick press release is reproduced below:

Astrophysicists at the University of Warwick have found that several Jupiter sized gas giants beyond our solar system have surface gravities much closer in strength to Earth than the intense gravity of Jupiter.

The University of Warwick team , Dr John Southworth, Dr Peter Wheatley and Giles Sams are the first people to calculate accurate measures of the surface gravity of all 14 known gas giant planets beyond our solar system that can be observed transiting (moving across the face of) their star. They created a new method which enabled the Warwick researchers to deduce the surface gravity of all 14 of these gas giants using a technique which is both simpler and ten times more accurate than an older method that had only produced a rough estimate for just one of the gas giants - HD 209458.

All but one of these 14 known gas giant planets that can be seen transiting their star have a planetary radius bigger than Jupiter. Intriguingly the one older surface gravity estimate available, for HD 209458, suggested it had a surface gravity of only 9.43 to 9.7 ms-2 . Despite being bigger than Jupiter this would give it a surface gravity closer to EarthΓ’Γ’β€šΒ¬Γ’β€žΒ’s at 9.8 ms-2 or our own solar systemΓ’Γ’β€šΒ¬Γ’β€žΒ’s smaller gas giants (Saturn 8.96 ms-2, Uranus 8.69 ms-2 and Neptune 11.15 ms-2 ) rather than Jupiter at 24.79 ms-2 .

On carrying out their more accurate measurement of all 14 of these gas giants the Warwick team have discovered that the surface gravity of HD 209458 is not an anomaly. Despite all but one of the gas giants (HD 149026) being bigger than Jupiter all but one of them turned out to have surface gravities that are much lower than JupiterΓ’Γ’β€šΒ¬Γ’β€žΒ’s. Only OGLE-TR-113 was found to have a surface gravity higher than JupiterΓ’Γ’β€šΒ¬Γ’β€žΒ’s.

In fact they found that 4 of these planets actually have surface gravities close to or lower than that of EarthΓ’Γ’β€šΒ¬Γ’β€žΒ’s or our own solar systemΓ’Γ’β€šΒ¬Γ’β€žΒ’s "smaller" gas giants rather than JupiterΓ’Γ’β€šΒ¬Γ’β€žΒ’s much more intense gravity. A further 4 had surface gravities around half to two thirds that of JupiterΓ’Γ’β€šΒ¬Γ’β€žΒ’s. For the planet for which there was already a rough estimate of surface gravity (HD209458b) they actually found an even lower surface gravity of 9.28 ms-2 (error factor of plus or minus 0.15 ms-2). A full table of their findings now follows:

Surface gravity values for the known transiting extra-solar planets.
linked-image


University of Warwick researcher John Southworth said: "This research gives us a sense of the sheer variety of types of planet to be found beyond our Solar System. An understanding of the surface gravity of these worlds also gives us a clearer picture of the rate of in the evaporation of planetary atmospheres."

Full paper online at http://uk.arxiv.org/PS_cache/arxiv/pdf/0704/0704.1570v1.pdf

* this last column in the table gives the weight that man who was 12 stone on the surface of the Earth would be if he stood the surface of each of those gas giant worldsΓ’Γ’β€šΒ¬Β¦. That is just before he sunk into the gaseous atmosphere and was suffocated and roasted to death of courseΓ’Γ’β€šΒ¬Β¦..

Source: University of Warwick Press Release
Edited by Waspie_Dwarf
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NASA Finds Extremely Hot Planet, Makes First Exoplanet Weather Map


Pasadena, Calif. – Researchers using NASA's Spitzer Space Telescope have learned what the weather is like on two distant, exotic worlds. One team of astronomers used the infrared telescope to map temperature variations over the surface of a giant, gas planet, HD 189733b, revealing it likely is whipped by roaring winds. Another team determined that the gas planet HD 149026b is the hottest yet discovered. Both findings appear May 9 in Nature.

linked-image
Image above: The first-ever map of the
surface of an exoplanet, or a planet beyond
our solar system.
Image credit: NASA/JPL-Caltech/
Harvard-Smithsonian CfA


"We have mapped the temperature variations across the entire surface of a planet that is so far away, its light takes 60 years to reach us," said Heather Knutson of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of the paper describing HD 189733b.

The two planets are "hot Jupiters" - sizzling, gas giant planets that zip closely around their stars. Roughly 50 of the more than 200 known planets outside our solar system, called exoplanets, are hot Jupiters. Visible-light telescopes can detect these strange worlds and determine certain characteristics, such as their sizes and orbits, but not much is known about their atmospheres or what they look like.

Since 2005, Spitzer has been revolutionizing the study of exoplanets' atmospheres by examining their infrared light, or heat. In one of the new studies, Spitzer set its infrared eyes on HD 189733b, located 60 light-years away in the constellation Vulpecula. HD 189733b is the closest known transiting planet, which means that it crosses in front and behind its star when viewed from Earth. It races around its star every 2.2 days.

linked-image
Image above: This artist's concept illustrates
the hottest planet yet observed in the universe.
Image credit: NASA/JPL-Caltech


Spitzer measured the infrared light coming from the planet as it circled around its star, revealing its different faces. These infrared measurements, comprising about a quarter of a million data points, were then assembled into pole-to-pole strips, and, ultimately, used to map the temperature of the entire surface of the cloudy, giant planet.

The observations reveal that temperatures on this balmy world are fairly even, ranging from 650 degrees Celsius (1,200 Fahrenheit) on the dark side to 930 degrees Celsius (1,700 Fahrenheit) on the sunlit side. HD 189733b, and all other hot Jupiters, are believed to be tidally locked like our moon, so one side of the planet always faces the star. Since the planet's overall temperature variation is mild, scientists believe winds must be spreading the heat from its permanently sunlit side around to its dark side. Such winds might rage across the surface at up to 9600 kilometers per hour (6,000 miles per hour). The jet streams on Earth travel at 322 kilometers per hour (200 miles per hour).

"These hot Jupiter exoplanets are blasted by 20,000 times more energy per second than Jupiter," said co-author David Charbonneau, also of the Harvard-Smithsonian Center for Astrophysics. "Now we can see how these planets deal with all that energy."

Also, HD 189733b has a warm spot 30 degrees east of "high noon," or the point directly below the star. In other words, if the high-noon point were in Seattle, the warm spot would be in Chicago. Assuming the planet is tidally locked to its parent star, this implies that fierce winds are blowing eastward.

In the second Spitzer study, astronomers led by Joseph Harrington of the University of Central Florida in Orlando discovered that HD 149026b is a scorching 2,038 degrees Celsius (3,700 Fahrenheit), even hotter than some low-mass stars. Spitzer was able to calculate the temperature of this transiting planet by observing the drop in infrared light that occurs as it dips behind its star.

"This planet is like a chunk of hot coal in space," said Harrington. "Because this planet is so hot, we believe its heat is not being spread around. The day side is very hot, and the night side is probably much colder."

HD 149026b is located 279 light-years away in the constellation Hercules. It is the smallest and densest known transiting planet, with a size similar to Saturn's and a core suspected to be 70 to 90 times the mass of Earth. It speeds around its star every 2.9 days.

According to Harrington and his team, the oddball planet probably reflects almost no starlight, instead absorbing all of the heat into its fiery body. That means HD 149026b might be the blackest planet known, in addition to the hottest.

"This planet is off the temperature scale that we expect for planets," said Drake Deming, a co-author of the paper, from NASA's Goddard Space Flight Center, Greenbelt, Md.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena.

For more information about the Spitzer Space Telescope, visit www.spitzer.caltech.edu or http://www.nasa.gov/spitzer.


Media contact: Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.


Source: NASA - Spitzer - News
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First Map of Alien World

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This is the first-ever map of the surface of an exoplanet, or a planet beyond our solar system. The map, which shows temperature variations across the cloudy tops of a gas giant called HD 189733b, is made up of infrared data taken by NASA's Spitzer Space Telescope. Hotter temperatures are represented in brighter colors.

HD 189733b is what is known as a hot-Jupiter planet. These sizzling, gas planets practically hug their stars, orbiting at distances that are much closer than Mercury is to our sun. They whip around their stars quickly; for example, HD 189733b completes one orbit in just 2.2 days. Hot Jupiters are also thought to be tidally locked to their stars, just as our moon is to Earth. This means that one side of a hot Jupiter always faces its star.

As predicted, the map reveals that HD 189733b has a warm spot on its "sunlit" side, which is always pointed toward the star. But the map also shows that this spot is offset from the high-noon, or sun-facing, point by 30 degrees. According to scientists, ferocious winds traveling up to 6,000 miles per hour (nearly 9,700 kilometers per hour) are probably pushing the hot spot to the east.

In addition to the warm spot, the map tells astronomers that temperatures on HD 189733b are fairly even all around. While the dark side is about 1,200 degrees Fahrenheit (650 degrees Celsius), the sunlit side is just a bit hotter at 1,700 degrees Fahrenheit (930 degrees Celsius). This mild temperature variation is more evidence for strong winds, since winds would help spread the heat from the hot, sunlit side over to the dark side.

These data were collected by Spitzer's infrared array camera as the planet, a so-called transiting planet, passed in front of its star, then swung around and disappeared behind it (see animation). By observing the planet for half of its 2.2-day long orbit, Spitzer was able to measure the infrared light, or heat, coming from its entire surface. The infrared measurements, about a quarter of a million individual data points, were then assembled by scientists into pole-to-pole strips, and ultimately into the complete map shown here.

Image credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA

+ High-resolution JPEG

Source: NASA - Spitzer - Multimedia

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Blacker than Black

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+ Play movie (Quicktime - 6Mb | Screen size: 640x480)

+ Play movie (Quicktime - 27Mb | Screen size: 1280x720)

This artist's concept illustrates the hottest planet yet observed in the universe. The scorching ball of gas, a "hot Jupiter" called HD 149026b, is a sweltering 3,700 degrees Fahrenheit (2,040 degrees Celsius) – about 3 times hotter than the rocky surface of Venus, the hottest planet in our solar system. The planet is so hot that astronomers believe it is absorbing almost all of the heat from its star, and reflecting very little to no light. Objects that reflect no sunlight are black. Consequently, HD 149026b might be the blackest known planet in the universe, in addition to the hottest.

The temperature of this dark and balmy planet was taken with NASA's Spitzer Space Telescope. While the planet reflects no visible light, its heat causes it to radiate a little visible and a lot of infrared light. Spitzer, an infrared observatory, was able to measure this infrared light through a technique called secondary eclipse. HD 149026b is what is known as a transiting planet, which means that it crosses in front of and passes behind its star – the secondary eclipse – when viewed from Earth. By determining the drop in total infrared light that occurs when the planet disappears, astronomers can figure out how much infrared light is coming from the planet alone.

The Spitzer observations of HD 149026b also suggest a hot spot in the middle of the side of the planet that always faces its star. Even though the planet is black, the spot would glow like a black lump of charcoal. HD 149026b is thought to be tidally locked, just as our moon is to Earth, such that one side of the planet is perpetually baked under the heat of its sun.

Astronomers think that HD 149026b is probably blazing hot on its sunlit side, and much cooler on its dark side. A similar phenomenon was observed previously by Spitzer for the planet Upsilon Andromedae b (http://www.spitzer.caltech.edu/Media/releases/ssc2006-18/index.shtml). In the case of both planets, heat is not being evenly distributed across their surfaces. This is the opposite of what happens on Jupiter, where temperature differences are minimal all around.

HD 149026b is located 256 light-years away in the constellation Hercules. It is the smallest known transiting planet, with a size similar to Saturn's and a suspected dense core 70 to 90 times the mass of Earth. It speeds around its star every 2.9 days.

Image credit: NASA/JPL-Caltech

+ High-resolution JPEG

Source: NASA - Spitzer - Multimedia

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NASA Develops Weather Map of a 'Hot Jupiter' Planet


Using images from the Spitzer Space Telescope, astronomers can now estimate the weather of a Jupiter-like exoplanet as it orbits a Sun-like star that is about 60 light-years away.

linked-image
Above: exoplanet artist renditionA

For the first time, scientists can map the atmosphere of a planet orbiting its parent star, by observing changes in the planet’s infrared brightness over time. The planet is tidally locked to its star like our moon is to Earth, which means that the same side of the planet always faces the star, and it is divided into permanent day and night. However, because the night side is nearly as hot as the day side, scientists say that fierce winds must be redistributing the heat from the starlit side to the dark side. In addition, the hottest part of the planet is shifted from the location that receives the most starlight. The results of this NASA-funded research will appear in the May 10 issue of the journal Nature.

β€œNow that we have this brightness/temperature map, we can learn a lot about this planet. We now believe that this planet is a very windy place; the speed of the west-to-east winds is probably several kilometers /second. We reached this conclusion because the brightest spot on the planet is not right in the middle of the map. The point in the middle of the map receives the most starlight, but it is not the hottest,” explained Jonathan Fortney, a planetary scientist at the Carl Sagan Center, Mountain View, Calif. who works at NASA Ames Research Center, Moffett Field, Calif. He is also a co-author of this study. ”The hottest (brightest) spot is offset by about 30 degrees, meaning that winds are blowing this hottest spot downstream.”

If there were no winds, the location on the planet that is permanently at high noon, with the blazing star directly overhead, would be hottest, as it constantly receives the most starlight. However, scientists have measured the hottest spot on this exoplanet, and it is 30 degrees to the east of the high noon spot. This means that the winds are so strong that they are blowing this hot gas about 25,000 miles away.

In the past, researchers have been able to detect the presence of planets outside our solar system, called extrasolar planets, and determine their size and location. Today, scientists use observations of infrared light (heat radiation) to determine atmospheric conditions and varying temperatures at different places on these planets.

weather mapping diagram For this study, scientists focused on a gas giant called HD 189733b, which is more than 30 times closer to its star than the Earth is to the Sun. It is a transiting planet, meaning it eclipses its parent star. Observations spanned slightly more than half of the planet’s orbit. As the day side of the planet rotated into view, scientists detected the increase in brightness and calculated its temperature range.

linked-image
Above: Scientists discovered that the brightest point in the middle of the
map is not the hottest point on the orbiting planet. The hottest spot is
offset from the brightest spot by about 30 degrees, meaning fierce winds
are blowing it downstream


According to scientists, a minimum brightness temperature of 1,200 degrees Fahrenheit occurs during the transit (when the planet moves in front of the star), and a maximum brightness temperature of 1,700 degrees Fahrenheit occurs about two hours before the planet moves behind the star. The difference in temperatures indicates that energy is being redistributed throughout the atmosphere.

β€œWhat we first observed was the infrared brightness of the planet when we saw the full night side and the planet eclipsed its star. Then we kept watching for 33 more hours as we gradually saw more and more of the day side. We eventually saw the full day side, just as the planet passed behind its parent star, like an anti-eclipse. Because we can measure the brightness of the planet as we gradually see more day and less night, we can break up the planet into slices and estimate the infrared brightness of each slice. We can then use this brightness map to calculate the temperature that would cause a given brightness,” Fortney said.

To study gas giant planets, atmosphere models are used to understand the contrast between day and night temperatures. Models of atmospheric chemistry help scientists understand where in the planet's atmosphere light is absorbed and emitted. Some important gases are water vapor, carbon monoxide, and atomic sodium and potassium. If estimates are accurate, scientists think that supersonic wind speeds exceeding four times the speed of sound may be necessary to transport the energy to the night side.

This work was made possible through funding by NASA as part of a long-term research program.

This study will appear in the May 10 issue of the journal Nature, 2007.

For further information, please visit:

http://www.nasa.gov/mission_pages/spitzer/main/index.html.


Ruth Marlaire
NASA Ames Research Center


Source: NASA/ARC - Research
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Mission Could Seek Out Spock's Home Planet


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Above left: Science fact - The SIM PlanetQuest mission will be able to detect habitable planets around other stars.
Above right: Science fiction - the Enterprise orbiting planet Vulcan.
(Star Trek images courtesy STARTREK.COM Copyright 2007 CBS Studios Inc.)


Science fiction may soon become science fact.

Astronomers at NASA's Jet Propulsion Laboratory have recently concluded that the upcoming planet-finding mission, SIM PlanetQuest, would be able to detect an Earth-like planet around the star 40 Eridani, a planet familiar to "Star Trek" fans as "Vulcan." 40 Eridani, a triple-star system 16 light-years from Earth, includes a red-orange K dwarf star slightly smaller and cooler than our sun. Vulcan is thought to orbit that dwarf star, called 40 Eridani A.

When pondering the idea that SIM might be able to detect Vulcan, astronomer Dr. Angelle Tanner at Caltech had two questions: Can a planet form around 40 Eridani A? Can SIM detect such a planet?

She consulted a planetary theorist, Dr. Sean Raymond of the University of Colorado, Boulder. "Since the three members of the triple star system are so far away from each other [hundreds of astronomical units - the Earth-Sun distance], I see no reason why an Earth-mass planet would not be able to form around the primary star, 40 Eridani A," he said.

If Vulcan life were to exist on the planet, the orbit of the planet would have to lie in a sweet spot around the star where liquid water could be present on its surface. Water is an essential ingredient for any organism to live long and prosper. For 40 Eridani A, this spot, or "habitable zone," is 0.6 astronomical units from the star. That means Vulcans would get to celebrate a birthday about every six months.

The SIM PlanetQuest instrument will be so accurate, it could measure the thickness of a nickel at a distance from Earth to the moon. Using a set of mathematical models based on Newton's Laws, Tanner was able to conclude that SIM would be able to definitively determine whether there is an Earth-mass planet orbiting in the habitable zone around 40 Eridani A, and could also determine its orbit.

This is quite an exciting prospect, since NASA's Terrestrial Planet Finder mission, planned for launch after SIM, would not only be able to take a rudimentary "picture" of the planet, but also could search for signatures of life such as methane and ozone.

linked-image
Image above: Artist's concept comparing our sun's habitable
zone with that of 40 Eridani.
+ Related animation


When asked what life would be like on Vulcan, Tanner speculated that the inhabitants might be pale. "A K dwarf star emits its light at wavelengths which are a bit redder compared to those from the sun, so I wonder whether it's harder to get a tan there," she said.

The results of Tanner's simulations will be submitted for publication in the Publications of the Astronomical Society of the Pacific.

For more information about NASA's search for new worlds, visit the PlanetQuest Web site at http://planetquest.jpl.nasa.gov.


Source: NASA - Exploring The Universe - New Worlds
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  • 2 weeks later...
Astronomers Discover Multi-Planet System; May Alter Theories of Planet Formation


The McDonald Observatory, University of Texas at Austin press release is reproduced below:

FORT DAVIS, Texas β€” University of Texas at Austin astronomers William Cochran and Michael Endl, working with graduate students Robert Wittenmyer and Jacob Bean, have used the 9.2-meter Hobby-Eberly Telescope (HET) at McDonald Observatory to discover a system of two Jupiter-like planets orbiting a star whose composition might seem to rule out planet formation. This NASA-funded study has implications for theories of planet formation.

Cochran and Endl have been monitoring the star, HD 155358, since 2001 using the High Resolution Spectrograph on HET. Their measurements of its β€œradial velocity,” or motion toward and away from Earth, show that the star has a wobble in its motion, which is caused by unseen companions tugging on the star.

HD 155358 is slightly hotter than the Sun, but a bit less massive. Most important, it only contains 20 percent as much of the chemical elements called β€œmetals” β€” elements heavier than hydrogen or helium β€” as the Sun. Along with one other star (called HD 47536), it contains the fewest metals of any star found to harbor planets.

Bean specializes in studying the metal contents of stars. His in-depth studies of the star’s spectrum revealed its metal-poor nature, and allowed him to deduce the star’s age of roughly10 billion years.

One planet has an orbital period of 195 days and, at a minimum, is 90 percent as massive as Jupiter. It orbits HD 155358 at a distance of 0.6 AU. (An astronomical unit, or AU, is the Earth-Sun distance of 150 million km, or 93 million miles.) The other planet orbits HD 155358 in 530 days, with a minimum mass half that of Jupiter, at a distance of 1.2 AU.

Wittenmyer used the University of Texas at Austin supercomputer β€œLonestar” to calculate the two massive planets’ orbits 100 million years into the future. The planets’ orbits are not circular, and they orbit close to each other and thus interact gravitationally β€” they push each other around.

β€œIt’s like a dance,” Endl said. He explained that β€œRob’s calculations show us how the orbits change over time: first more eccentric, then more circular, and back again.” The system is stable, Endl said, and the pattern repeats about every 3,000 years.

According to Wittenmyer, β€œThe planets are trading eccentricity with each other. When one orbit is more circular, the other is more eccentric.”

The combination of massive planets orbiting a metal-poor star has consequences for theories of planet formation.

β€œThere are two competing planet-formation models,” Endl said. Those models are known as the β€œcore accretion model” and the β€œdisk instability model.”

Both models start with a rotating cloud with a star forming at its center. As it rotates, the cloud flattens into a disk. Over time, dust in the disk begins to clump together to form the seeds that will eventually become planets. Where the two models differ is in terms of timescale.

In the core accretion model, a Jupiter-like planet forms in a two-step process. Over about a million years, a proto-planetary β€œcore” several times the mass of Earth forms through gravitational accumulation of solid materials. When it reaches this mass, it has enough gravity to then pull huge amounts of gas onto itself. Over several million more years, it grows into a gas giant planet.

This model relies on large amounts of heavy elements to be present in the disk β€” and, of course, in the starβ€” to form the cores, Endl said.

β€œMost of the planets found using the radial velocity technique are found around metal-rich stars,” he said. β€œThat argues for the β€˜core accretion’ model. Many astronomers in this field agree that the higher fraction of planets around metal-rich stars is supporting evidence for the core-accretion model.”

”Having this process happen to form not just one, but two, planets around a star that had so little solid material available for planet-building is quite remarkable.” Cochran said.

The competing model of planet formation is called the disk instability model. It argues that the rotating disk of gas and dust around the forming star becomes unstable very soon after the disk forms, causes the disk to break into giant clumps. Gravity within each clump can cause the gas to collapse under its own gravity, forming giant planets in only several hundred years.

β€œGas giant planets formed this way might not have any solid core at all,” Endl said.

Cochran and his colleagues argue that HD 155358 could have formed the two planets through either method of planet formation.

β€œThe major result of our discovery is that these planets required a very massive disk to form, several times more massive than we think our solar system disk was,” Endl said. β€œThis demonstrates that disk masses can vary significantly and might even be the most crucial factor in planet formation.”

Cochran and colleagues first began using radial velocity techniques to search for planets from McDonald Observatory in the late 1980s, using the 2.7-meter Harlan J. Smith Telescope. The program continues today on both the Smith Telescope and HET, and Cochran’s team has found planets orbiting several stars.

The Hobby-Eberly Telescope is a joint project of The University of Texas at Austin, The Pennsylvania State University, Stanford University, Ludwig-Maximilians-UniversitΓ€t MΓΌnchen and Georg-August-UnversitΓ€t GΓΆttingen.

β€” END β€”

Note : More information is available online here.


Source: McDonald Observatory Press Release
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Just goes to show we still have a lot to learn about the mechanics involved in planetary formation... IMO

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Just goes to show we still have a lot to learn about the mechanics involved in planetary formation... IMO

Very true. As is often the case in science the more you know the more questions you are left with.

Until 1992 the planets of our solar system were the only ones we knew about. Astronomers thought that the could explain the formation of the solar system reasonably well and had no reason to think that it wasn't typical of what would be found.

Then in 1992 the very first exo planet was found. Much to the surprise of the astronomical community it was found in orbit around a pulsar. As this was such a different situation to the solar system it didn't really alter the theories on normal planet creation (pulsar planets are believed to form from the debris of the supernova explosion that formed the pulsar).

In 1995 we had the first discovery of a planet orbiting a normal star. This was the first of the,so-called, hot-Jupiters. Of the 237 or so exo-planets found so far are hot-Jupiters or hot-Neptunes. These are large planets orbiting close to their sun. Such planets were not widely expected just over a decade ago.

As we do not yet have the ability to discover an Earth sized planet in an Earth like orbit we are left with a question. Do we live in an unusual solar system, with Hot-Jupiters being the dominant planet type or will we discover lots of Earth like worlds when the technology improves?

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California, Carnegie team reports 28 new exoplanets, 7 new brown dwarfs


The UC Berkley press release is reproduced below:

By Robert Sanders, Media Relations | 29 May 2007

BERKELEY – The world's largest and most prolific team of planet hunters announced Monday, May 28, the discovery of 28 new planets outside our solar system, increasing to 236 the total number of known exoplanets.

linked-image
An artist's concept of the Neptune-sized planet GJ436b (right) orbiting
an M dwarf star, Gliese 436, at a distance of only 3 million miles. With
a density similar to that of Neptune, the exoplanet is an ice giant and
probably has a rocky core and lots of water that forms ice in the
interior under high pressure and temperature. GJ436b was discovered
in 2004 by the California and Carnegie Planet Search team, and
found by Belgian astronomer MichaΓ«l Gillon in May 2007 to transit its
star.
(Illustrations Copyright Lynnette Cook)


University of California, Berkeley, post-doctoral fellow Jason T. Wright and newly minted Ph.D. John Asher Johnson reported the new exoplanets at a media briefing at the semi-annual meeting of the American Astronomical Society (AAS) in Honolulu. The findings, also reported in poster sessions at the meeting, are a result of the combined work of the California and Carnegie Planet Search team and the Anglo-Australian Planet Search team.

The planets are among 37 new objects - each orbiting a star, but smaller than a star -discovered by the teams within the past year. Seven of the 37 are confirmed brown dwarfs, which are failed stars that nevertheless are much more massive than the largest, Jupiter-sized planets. Two others are borderline and could be either large, gas giant planets or small brown dwarfs.

Wright said the research teams have become much more sophisticated in their analyses of the stellar wobbles caused by orbiting planets, enabling them to detect the weaker wobbles caused by smaller planets as well as planets farther from their parent stars.

"We've added 12 percent to the total in the last year, and we're very proud of that," said Wright of the 28 new exoplanets. "This provides new planetary systems so that we can study their properties as an ensemble."

The California and Carnegie Planet Search team is headed by Geoffrey Marcy, professor of astronomy at UC Berkeley; Paul Butler of the Carnegie Institution of Washington; Debra Fischer of San Francisco State University; and Steve Vogt, professor of astronomy at UC Santa Cruz. The Anglo-Australian Planet Search team is headed by Chris Tinney of the University of New South Wales and Hugh Jones of the University of Hertfordshire. They and colleagues Shannon Patel of UC Santa Cruz and Simon O'Toole of the Anglo-Australian Observatory have published their exoplanet results in papers over the past year, but the AAS meeting is the first time the teams have presented the past year's findings in their entirety.
exoplanet in transit around star

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The ice giant planet GJ436b is like a hot-Neptune
that orbits Gliese 436 every 2.6 days. Because we
view its orbit edge-on, the planet often transits the
star, as in this artist's rendering.


In addition to reporting 37 new substellar objects, Wright singled out an exoplanet discovered by their teams two years ago as "extraordinarily rich." Circling the star Gliese 436 (GJ 436), a red M dwarf only 30 light years from Earth, was an ice-giant planet the teams calculated to be at least 22 Earth masses, slightly larger than the mass of Neptune (17 Earth masses). After the discovery in 2004 and publication of the exoplanet's orbit earlier this year, a Belgian astronomer, Michael Gillon at Liege University, observed the planet crossing in front of the star - the first Neptune-sized planet observed to transit a star. Gillon and colleagues reported two weeks ago how this transiting planet allowed them to precisely pin down the mass, 22.4 Earth masses, and to calculate the planet's radius and density, which turns out to be similar to Neptune's.

"From the density of two grams per cubic centimeter - twice that of water - it must be 50 percent rock and about 50 percent water, with perhaps small amounts of hydrogen and helium," Marcy said. "So this planet has the interior structure of a hybrid super-Earth/Neptune, with a rocky core surrounded by a significant amount of water compressed into solid form at high pressures and temperatures."

Its short, 2.6-day orbit around Gliese 436 means the exoplanet is very close to the star - only 3 percent of the sun-Earth distance - making it a hot Neptune, Wright said. It also has an eccentric orbit, not a circular orbit like most giant planets found orbiting close to their parent stars. This orbit, in fact, suggests that the star may have another planetary companion in a more distant orbit.
drawing of exoplanet interior

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Drawing of the predicted interior of an ice-giant planet like GJ436b
or Neptune.
(Credit: Jason Wright/UC Berkeley)


"I'm sure people will immediately follow up and try to measure the atmospheric composition of this planet." Wright predicted.

Also among the 28 new exoplanets are at least four new multiple-planet systems, plus three stars that probably contain a brown dwarf as well as a planet. Wright said that at least 30 percent of all stars known to have planets have more than one. Because smaller planets and outer planets of a star are harder to detect, he predicts that the percentage will continue to rise as detection methods improve.

"We're just now getting to the point where, if we were observing our own solar system from afar, we would be seeing Jupiter," he said, pointing out that the teams' Doppler technique is now sensitive to stellar wobbles of a meter per second, much less than the 10-meter per second limit they started out with 15 years ago.

Wright keeps track of all known exoplanets for the California and Carnegie Planet Search team's Web site, http://exoplanets.org, which hosts the only peer-reviewed catalog of exoplanets within 200 parsecs (652 light years) of Earth. This includes "everything that is close enough to study and possibly follow up with imaging," he said.

Three of the newly reported planets are around large stars between 1.6 and 1.9 times the mass of our sun. Johnson has focused on exoplanets around massive stars, known as A and F stars, which have masses between 1.5 and 2.5 solar masses. Planets around these massive stars are normally very hard to detect because they typically rotate fast and have pulsating atmospheres, traits that can hide or mimic the signal from an orbiting planet. He discovered, however, that cooler "retired" A stars - "subgiant" stars that have nearly completed hydrogen burning and have stabilized for a short period of time - are quiet enough to make planet-caused wobbles detectable.

So far, Johnson has tracked down six previously discovered exoplanets around retired A stars, and by combining this set with the three newly discovered exoplanets, has been able to draw preliminary conclusions. For one, planets around more massive stars seem to be farther from their host stars, Johnson said.

"Only one of the 9 planets is within 1 AU (astronomical unit, or 93 million miles), and none of them is within 0.8 AU, of their host stars, which is very different than the distribution around sun-like stars," he said, noting that many sun-like stars harbor hot gas giants that whip around their host stars in two to 100 days. Even though short-period planets are easier to detect, no such planets have been detected orbiting retired A stars, whose typical planets have an orbital distance about equal to Earth's orbit or greater, with an orbital period of a few years.

Based on the results of his search for planets around retired A stars, Johnson has discovered that massive stars are more likely to harbor Jupiter-sized planets than are lower-mass stars. The chance of having a Jupiter-like, giant planet orbiting within 2 AU is 8.7 percent for stars between 1.3 and 2 solar masses, versus 4 percent for sun-like stars with masses ranging from 0.7 solar masses to 1.3 solar masses, and 1.2 percent for M stars with less than 0.7 solar masses. As would be expected from the core accretion model of planet formation, large planets are more often observed around massive stars, probably because these stars start out with more material in their disks during the early formation period.

Johnson will continue to focus on retired A stars, 450 of which have been added to the teams' target list. As more planets are discovered around subgiants, it should become clearer whether larger orbits are "a result of different formation and migration mechanisms in the disks of A-type stars, or simply a consequence of the small number of massive subgiants currently surveyed," he and colleagues wrote in a paper submitted in April to the Astrophysical Journal.

The California and Carnegie Planet Search team uses telescopes at the University of California's Lick Observatory and the W. M. Keck Observatory in Hawaii. The Anglo-Australian Planet Search team uses the Anglo-Australian Observatory. Together, these teams have discovered more than half of all known exoplanets.

The work is funded by the National Aeronautics and Space Administration, the National Science Foundation, the W. M. Keck Observatory, the Carnegie Institution of Washington, the Anglo-Australian Observatory and the UC Observatories.


Source: UC Berkley Press Release
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Massive Transiting Planet with 31-hour Year Found Around Distant Star


The Lowell Observatory press release is reproduced below:

For Immediate Release
May 31, 2007

Flagstaff, Ariz.– An international team of astronomers with the Trans-atlantic Exoplanet Survey today announce the discovery of their third planet, TrES-3. The new planet was identified by astronomers looking for transiting planets – that is, planets that pass in front of their home star – using a network of small automated telescopes in Arizona, California, and the Canary Islands. TrES-3 was discovered in the constellation Hercules about 10 degrees west of Vega, the brightest star in the summer skies.

"TrES-3 is an unusual planet as it orbits its parent star in just 31 hours!," said Georgi Mandushev, Lowell Observatory astronomer. "That is to say, the year on this planet lasts less than one and a third days. It is also a very massive planet – about twice the mass of the solar system's biggest planet, Jupiter – and is one of the planets with the shortest known periods."

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Figure 1:

A computer-generated simulation of TrES-3 as seen from the night side, with its host star in the distance. The planet's home star is slightly smaller and cooler than the Sun, and is about six times larger than the planet. TrES-3 is a gas giant, similar to our own Jupiter but about 30 percent bigger and about twice as massive. Unlike Jupiter, however, TrES-3 is very close to its parent star and orbits it in 31 hours. That means that the year on TrES-3 lasts less than one and one-third Earth days.

Credit: Jeffrey Hall, Lowell Observatory


The new planet TrES-3 was first noticed by Lowell Observatory's Planet Search Survey Telescope (PSST), set up and operated by Edward Dunham and Georgi Mandushev. The Sleuth telescope, maintained by David Charbonneau (CfA) and Francis O'Donovan (Caltech), at Caltech's Palomar Observatory also observed transits of TrES-3, confirming the initial detections. TrES-3 is about 800 light-years distant and because it is so close to its host star, it is very hot, about 1,500 degrees Kelvin.

"TrES-3 will be an intriguing object to study more deeply, said Edward Dunham, Lowell Observatory instrument scientist. "For example, its tight orbit causes it to be illuminated very strongly. This may make it possible to measure the variation in reflected light as it goes through its phases. This will tell us how reflective its atmosphere is."

By definition, a transiting planet passes directly between Earth and the star, causing a slight dimming of the star's light in a manner similar to that caused when the moon passes between the Sun and Earth during a solar eclipse. To look for transits, the small telescopes are automated to take wide-field timed exposures of the clear skies on as many nights as possible. When an observing run is completed for a particular field β€” usually over an approximate two-month period β€” astronomers measure very precisely the light from every star in the field in order to detect the possible signature of a transiting planet. "TrES-3 blocks off about 2.5 percent of the light of the star as it passes in front of it," said Mandushev. "With our telescopes, we can measure this tiny drop in the star's brightness and deduce the presence of a planet there."

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Figure 2:

A computer-generated simulation of TrES-3 crossing (transiting) the disk of its host star. TrES-3 transits farther from the disk center than any other known transiting planet. The transit of TrES-3 causes a drop in the brightness of its home star of about two and a half percent. This slight dimming of the star's light was noticed and measured by the TrES researchers, who used the parameters of the transit to determine the planet's mass, size and other properties.
Credit: Jeffrey Hall, Lowell Observatory


TrES-3 was also observed by members of the Hungarian Automated Telescope Network (HATNet). The study's lead author, Francis O'Donovan of Caltech, highlighted the teamwork between TrES and HAT. "The search for extrasolar planets is an exciting and competitive field. I was happy to see that cooperation between separate teams led to a rapid confirmation of this planet," said O'Donovan.

In order to help confirm they had found a planet, HATNet's Gaspar Bakos and CfA's Guillermo Torres switched from the 10-centimeter TrES telescopes to one of the 10-meter telescopes at the W. M. Keck Observatory on the summit of Mauna Kea, Hawaii. Using this giant telescope, they confirmed that they had found a new planet. In order to measure accurately the size and other properties of TrES-3, astronomers also made follow up observations of it with bigger telescopes at Lowell Observatory and Fred L. Whipple Observatory in Arizona, and with the Las Cumbres Observatory Global Telescope in Hawaii.

Other authors of the paper "TrES-3: A Nearby, Massive, Transiting Hot Jupiter in a 31-hour Orbit," accepted for publication in the Astrophysical Journal, are Gaspar Bakos, David Charbonneau, David Latham, Alessandro Sozzetti, Robert Stefanik, and Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics; Timothy Brown, Nairn Baliber, and Marton Hidas of the Las Cumbres Observatory Global Telescope; Geza Kovacs of Konkoly Observatory in Hungary; Mark Everett and Gilbert Esquerdo of the Planetary Science Institute; Markus Rabus, Hans Deeg, and Juan Belmonte of the Instituto de Astrofisica de Canaries in Tenerife, Spain; and Lynne Hillenbrand of the California Institute of Technology. The paper is available online at: http://arxiv.org/abs/0705.2004.

This research is funded by NASA through the Origins of Solar Systems Program.

end


contact:

Steele Wotkyns
Public Relations Manager
(928) 233-3232
steele@lowell.edu

and

Georgi Mandushev
Astronomer
(928) 233-3252
gmand@lowell.edu

About Lowell Observatory

Lowell Observatory is a private, non-profit research institution founded in 1894 by Percival Lowell. The Observatory has been the site of many important findings including the discovery of the large recessional velocities (redshift) of galaxies by Vesto Slipher in 1912-1914 (a result that led ultimately to the realization the universe is expanding), and the discovery of Pluto by Clyde Tombaugh in 1930. Today, Lowell's 19 astronomers use ground-based telescopes around the world, telescopes in space, and NASA planetary spacecraft to conduct research in diverse areas of astronomy and planetary science. Lowell Observatory currently has four research telescopes at its Anderson Mesa dark sky site east of Flagstaff, Arizona, and is building a 4-meter class research telescope, the Discovery Channel Telescope, in partnership with Discovery Communications, Inc.

Source: Lowell Observatory Press Release
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As we do not yet have the ability to discover an Earth sized planet in an Earth like orbit we are left with a question. Do we live in an unusual solar system, with Hot-Jupiters being the dominant planet type or will we discover lots of Earth like worlds when the technology improves?

Without finding even more planets (yeah, several hundred sounds like a lot, but considering how many planetary systems β€˜might’ exist, it really isn’t), trying to find some pattern could be misleading... IMO

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Without finding even more planets (yeah, several hundred sounds like a lot, but considering how many planetary systems Γ’β‚¬ΛœmightÒ€ℒ exist, it really isnÒ€ℒt), trying to find some pattern could be misleading... IMO

That was exactly my point, although it doesn't stop astronomers asking the questions. It also doesn't stop them coming to some preliminary conclusions based on the currently available information.

Hot Jupiters were not predicted by the current theories of planetary formation. A gas giant forming that close to its parent star should have its atmosphere ripped away when the nuclear fusion starts at the suns core. To confuse the issue even more, observations of young stars with rings of debris around them seem to confirm the theory of planet formation.

This leaves us with an apparent paradox. We have the confirmation of a theory that says hot Jupiters shouldn't exist but we also have hot Jupiters. The current explanation is that the hot Jupiters form further out from the star (in orbits similar to Jupiter and Saturn in our own solar system). Hence they are far enough away for their atmospheres to survive the star's ignition. However their is still sufficient dust and gas around the star to slow the planet down in its orbit. This will cause it to get closer and closer to the star until it arrives in the orbit we see it in today. Any rocky planets which have formed closer to the star will also fall inwards, however they will fall into the star and be destroyed.

The huge number of hot Jupiters and hot Neptunes being found implies that this process is quite common. The other side of the coin is that if hot Jupiters are formed this way and are common then terrestrial planets will be fairly rare.

We will begin to know the answers in a few years. The one thing I would bet on is that there will be a lot more surprises ahead.

Edited by Waspie_Dwarf
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Boring Star May Mean Livelier Planet: UBC Astronomer


The University of British Columbia press release is reproduced below:

Media Release | Jun. 8, 2007

Ò€œBoringÒ€ light from red dwarf star Gliese 581 means better odds for extraterrestrial life in that planetary system, according to University of British Columbia astronomer Jaymie Matthews.

Approximately 20.5 light years from the Earth, Gliese 581 made the headlines in April 2007 when European scientists discovered a planet, named Gliese 581c. Dubbed Ò€œsuperEarth,Ò€ the planet orbits Gliese 581 and could have water -- and thus able to support life.

Ò€œThe Gliese 581 system is the first to be found -- beyond our own Earth -- that might have a liveable planet,Ò€ said Matthews.

Using Canada Space AgencyÒ€ℒs suitcase-sized space telescope, the Microvariability and Oscillations of STars (MOST), Matthews put Gliese 581 on a six-week scientific stakeout following the April discovery. He will present his findings today at the Canadian Astronomical SocietyÒ€ℒs annual meeting in Kingston, Ontario.

Matthews and his team searched for the subtle dips in the light from the star when the planetÒ€ℒs orbit carried it directly between the star and the Earth, resulting in a Ò€œmini-eclipseÒ€ every 13 days. The depth of the dips would help researchers determine the size of the planet Gliese 581c, while the behaviour of the starlight at other times would help astronomers gauge the suitability of Gliese 581 as a Ò€œhome star,Ò€ a star able to sustain life on planets around it.

Ò€œGliese 581 seems remarkably stable over the six weeks it was monitored by MOST,Ò€ said Matthews. Ò€œThe brightness of the star changed by only a few tenths of a percent over that time. This level of stability means that it provides a stable source of light -- hence heat -- to the surface of planet Gliese 581c.

Ò€œThe climate there should not be a wild rollercoaster ride that would make it difficult for life to get a foothold,Ò€ said Matthews. Ò€œIt also suggests the star is quite old, and settled in its ways, and that the planets around it have probably been around for billions of years.Ò€

It took approximately 3.5 billion years for life on Earth to reach the level of complexity that we call human, said Matthews. Ò€œSo if Gliese 581 has been around for at least that long, itÒ€ℒs more encouraging for the prospects of complex life on any planet around it.Ò€

With space missions like MOST, the French satellite COROT, which joined MOST in orbit late last December, and the American Kepler mission due for launch in November 2008, Matthews predicts that other Γ’β‚¬ΛœEarthyÒ€ℒ worlds will come to light in the coming months and years.

Ò€œSome of them will have orbits that produce planetary alignments,Ò€ said Matthews. Ò€œNot the kind that excites somebody reading a horoscope but the kind thatÒ€ℒs exciting for astronomers because they will allow us to test our models of alien worlds -- worlds that might be homes to neighbours in our Galactic city, the Milky Way.Ò€

MOST is a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute for Aerospace Studies and the University of British Columbia, with the assistance of the University of Vienna. For more information, visit www.astro.ubc.ca/MOST.


Source: UBC Press Release Edited by Waspie_Dwarf
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Hidden Planet Pushes Star's Ring a Billion Miles Off-Center


The University of Rochester press release is reproduced below:

June 11, 2007

A young star's strange elliptical ring of dust likely heralds the presence of an undiscovered Neptune-sized planet, says a University of Rochester astronomer in the latest Monthly Notices of the Royal Astronomical Society.

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Hubble image of Fomalhaut ring

Stars in the early stages of life are surrounded by dust clouds that thin out and dissipate as the star reaches maturity, becoming rings in their final stages. One star, however, has a dust ring that has long puzzled astronomers because it is not centered around the star as usual. Instead, the ring is elliptical, with the parent star off to one side.

"We wanted to know why this ring was off-center," says Alice C. Quillen, Associate Professor of Astronomy and author of the study. "People guessed there might be a planet in there, but nobody knew where it might be, or how big it might be. Now we've got a very good idea."

Roughly 250 planets have been discovered so far around stars other than our Sun. Most have been revealed by the way the planets influence their parent stars, but Quillen has been working for years on understanding the delicate interaction between stellar dust disks and the planets that shape them. She is now one of the world's experts in predicting planet size and position from the features of a star's dust ring.

Quillen used new images from the Hubble Space Telescope that caught the star, Fomalhaut, and its surrounding ring almost edge-on and in more detail than ever before. Fomalhaut, 25 light-years away, is the brightest star in the autumn sky. Using a device called a coronagraph that blocks out a star's light so dimmer objects near it can be seen, the Hubble revealed that Fomalhaut was indeed off-center within its ring. The images were also clear enough to show that the ring itself had a surprisingly sharp edge.

That sharp edge was the clue Quillen was looking for. Since ascertaining one of the first extra-solar planets using dust-ring analysis in 2002, Quillen has greatly strengthened her planet-ring interaction models. Treating the ring like a hydrodynamic structure, for instance, is necessary for younger stars whose dust is relatively fine and acts more like a fluidβ€”while the physics of dust collision become dominant in older ring systems where the dust has begun clumping into larger bodies.

The sharp inside edge of Fomalhaut, Quillen calculated, demanded that a relatively small, Neptune-size planet was tucked right up against the inner side of the ring, using its gravity to toss dust in the area out of orbit.

According to Quillen's calculations, the ring is elliptical because the Neptunian planet's own orbit around Fomalhaut is ellipticalβ€”a curiosity in such a young system. When stars form from a giant cloud of gas and dust, the angular momentum of the cloud carries over to all the objects that form from the cloud, including new planets. Those new planets should, initially at least, orbit in nice, circular pathsβ€”not elliptical ones. Fomalhaut's ring is offset by 1.4 billion miles, more than 15 times the distance from the Earth to the Sun, suggesting the hidden planet's orbit is also tremendously skewed.

"Something had to skew that planet, and that's what we're working on now," says Quillen. "There may have been fantastic planetary collisions early on that changed their orbits. We're working on figuring out how many more planets of what size you'd need to account for that elliptical orbit, and to account for why there is no other dust inside that ring."

Quillen's model will remain just a theory until a new generation of telescopes can actually see the Formalhaut planets in question. These telescopes will be equipped with sophisticated coronagraphs that can block out Formalhaut's light enough to let the planets themselves shine through.

This research was funded by the National Institutes of Science and NASA.

Source: University of Rochester Press Release
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  • 4 weeks later...
NASA's Spitzer Finds Water Vapor on Hot, Alien Planet


For Release: July 11, 2007

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A scorching-hot gas planet beyond our solar system is steaming up with water vapor, according to new observations from NASA's Spitzer Space Telescope.

The planet, called HD 189733b, swelters as it zips closely around its star every two days or so. Astronomers had predicted that planets of this class, termed "hot Jupiters," would contain water vapor in their atmospheres. Yet finding solid evidence for this has been slippery. These latest data are the most convincing yet that hot Jupiters are "wet."

"We're thrilled to have identified clear signs of water on a planet that is trillions of miles away," said Giovanna Tinetti, a European Space Agency fellow at the Institute d'Astrophysique de Paris in France. " Tinetti is lead author of a paper on HD 189733b appearing today in Nature.

Although water is an essential ingredient to life as we know it, wet, hot Jupiters are not likely to harbor any creatures. Previous measurements from Spitzer indicate that HD 189733b is a fiery 1,000 Kelvin (1,340 degrees Fahrenheit) on average. Ultimately, astronomers hope to use instruments like those on Spitzer to find water on rocky, habitable planets like Earth.

"Finding water on this planet implies that other planets in the universe, possibly even rocky ones, could also have water," said co-author Sean Carey of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena. "I'm excited to tell my nephews and niece about the discovery."

The new findings are part of a brand new field of science investigating the climate on exoplanets, or planets outside our solar system. Such faraway planets cannot be seen directly; however, in the past few years, astronomers have begun to glean information about their atmospheres by observing a subset of hot Jupiters that transit, or pass in front of, their stars as seen from Earth.

Earlier this year, Spitzer became the first telescope to analyze, or break apart, the light from two transiting hot Jupiters, HD 189733b and HD 209458b. One of its instruments, called a spectrometer, observed the planets as they dipped behind their stars in what is called the secondary eclipse. This led to the first-ever "fingerprint," or spectrum, of an exoplanet's light. Yet, the results came up "dry," probably because the structure of these planets' atmospheres makes finding water with this method difficult.

Later, a team of astronomers found hints of water in HD 209458b by analyzing visible-light data taken by NASA's Hubble Space Telescope. The Hubble data were captured as the planet crossed in front of the star, an event called the primary eclipse.

Now, Tinetti and her team have captured the best evidence yet for wet, hot Jupiters by watching HD 189733b's primary eclipse in infrared light with Spitzer. In this method, changes in infrared light from the star are measured as the planet slips by, filtering starlight through its outer atmosphere. The astronomers observed the eclipse with Spitzer's infrared array camera at three different infrared wavelengths and noticed that for each wavelength a different amount of light was absorbed by the planet. The pattern by which this absorption varies with wavelength matches that created by water.

"Water is the only molecule that can explain that behavior," said Tinetti. "Observing primary eclipses in infrared light is the best way to search for this molecule in exoplanets."

The water on HD 189733b is too hot to condense into clouds; however, previous observations of the planet from Spitzer and other ground and space-based telescopes suggest that it might have dry clouds, along with high winds and a hot, sun-facing side that is warmer than its dark side. HD 189733b is located 63 light-years away in the constellation Vulpecula.

Other authors of the Nature paper include Alfred Vidal-Madjar, Jean-Phillippe Beaulieu, David Sing and Nicole Allard of the Institute d'Astrophysique de Paris: Mao-Chang Liang of Caltech and the Academia Sinica, Taiwan; Yuk Yung of Caltech; Robert J. Barber and Jonathan Tennyson of University College London in England; Ignasi Ribas of the Institut de Ciències de l'Espai, Spain; Gilda E. Ballester of the University of Arizona, Tucson; and Franck Selsis of the Ecole Normale Supérieure, France. JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, Pasadena. JPL is a division of Caltech. Spitzer's infrared array camera was built by NASA's Goddard Space Flight Center, Greenbelt, Md. The instrument's principal investigator is Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

jpl2007-077
ssc2007-12


Source: NASA/CalTech - Spitzer- Newsroom
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Credit: ESA, NASA/ JPL-Caltech/G. Tinetti (Institute d'Astrophysique de Paris, University College London)

Exoplanet Forecast: Hot and Wet

This plot of data from NASA's Spitzer Space Telescope tells astronomers that a toasty gas exoplanet, or a planet beyond our solar system, contains water vapor.

Spitzer observed the planet, called HD 189733b, cross in front of its star at three different infrared wavelengths: 3.6 microns, 5.8 microns, and 8 microns (see lime-colored dots). For each wavelength, the planet's atmosphere absorbed different amounts of the starlight that passed through it. The pattern by which this absorption varies with wavelength matches known signatures of water, as shown by the theoretical model in blue.

Source: NASA/CalTech - Spitzer- Newsroom

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  • 2 weeks later...
Planets with Four Parents? Spitzer Finds Evidence for Strange Stellar Family


Written by Linda Vu, Spitzer Science Center
July 24, 2007


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How many stars does it take to "raise" a planet? In our own solar system, it took only one -- our Sun. However, new research from NASA's Spitzer Space Telescope shows that planets might sometimes form in systems with as many as four stars.

Astronomers used Spitzer's infrared vision to study a dusty disk that swirls around a pair of stars in the quadruple-star system HD 98800. Such disks are thought to give rise to planets. Instead of a smooth, continuous disk, the telescope detected gaps that could be caused by a unique gravitational relationship between the system's four stars. Alternatively, the gaps could indicate planets have already begun to form, carving out lanes in the dust.

"Planets are like cosmic vacuums. They clear up all the dirt that is in their path around the central stars," said Dr. Elise Furlan, of the NASA Astrobiology Institute at the University of California at Los Angeles. Furlan is the lead author of a paper that has been accepted for publication in The Astrophysical Journal.

HD 98800 is approximately 10 million years old, and is located 150 light-years away in the constellation TW Hydrae.

Before Spitzer set its gaze on HD 98800, astronomers had a rough idea of the system's structure from observations with ground-based telescopes. They knew the system contains four stars, and that the stars are paired off into doublets, or binaries. The stars in the binary pairs orbit around each other, and the two pairs also circle each other like choreographed ballerinas. One of the stellar pairs, called HD 98800B, has a disk of dust around it, while the other pair has none.

Although the four stars are gravitationally bound, the distance separating the two binary pairs is about 50 astronomical units (AU) -- slightly more than the average distance between our Sun and Pluto. Until now, technological limitations have hindered astronomers' efforts to look at the dusty disk around HD 98800B more closely.

With Spitzer, scientists finally have a detailed view. Using the telescope's infrared spectrometer, Furlan's team sensed the presence of two belts in the disk made of large dust grains. One belt sits at approximately 5.9 AU away from the central binary, HD 98800B, or about the distance from the Sun to Jupiter. This belt is likely made up of asteroids or comets. The other belt sits at 1.5 to 2 AU, comparable to the area where Mars and the asteroid belt sit, and probably consists of fine grains.

"Typically, when astronomers see gaps like this in a debris disk, they suspect that a planet has cleared the path. However, given the presence of the diskless pair of stars sitting 50 AU away, the inward-migrating dust particles are likely subject to complex, time-varying forces, so at this point the existence of a planet is just speculation," said Furlan.

Astronomers believe that planets form like snowballs over millions of years, as small dust grains clump together to form larger bodies. Some of these cosmic rocks then smash together to form rocky planets, like Earth, or the cores of gas-giant planets like Jupiter. Large rocks that don't form planets often become asteroids and comets. As these rocky structures violently collide, bits of dust are released into space. Scientists can see these dust grains with Spitzer's supersensitive infrared eyes.

According to Furlan, the dust generated from the collision of rocky objects in the outer belt should eventually migrate toward the inner disk. However, in the case of HD 98800B, the dust particles do not evenly fill out the inner disk as expected, due to either planets or the diskless binary pair sitting 50 AU away and gravitationally influencing the movement of dust particles.

"Since many young stars form in multiple systems, we have to realize that the evolution of disks around them and the possible formation of planetary systems can be way more complicated and perturbed than in a simple case like our solar system," Furlan added.

Multiple-star planets would also have interesting sunsets. For more information about planets with double and triple sunsets, see the story "NASA Telescope Finds Planets Thrive Around Stellar Twins" and "NASA Scientist Finds World With Triple Sunsets."


Source: NASA/CalTech - Spitzer- Newsroom
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NASA/JPL-Caltech/T. Pyle (SSC)

Evidence for Strange Stellar Family

This artist concept depicts a quadruple-star system called HD 98800. The system is approximately 10 million years old, and is located 150 light-years away in the constellation TW Hydrae.

HD 98800 contains four stars, which are paired off into doublets, or binaries. The stars in the binary pairs orbit around each other, and the two pairs also circle each other like choreographed ballerinas. One of the stellar pairs, called HD 98800B, has a disk of dust around it, while the other pair does not.

Although the four stars are gravitationally bound, the distance separating the two binary pairs is about 50 astronomical units (AU) -- slightly more than the average distance between our sun and Pluto.

Using NASA's Spitzer Space Telescope, scientists finally have a detailed view of HD 98800B's potential planet-forming disk. Astronomers used the telescope's infrared spectrometer to detect the presence of two belts in the disk made of large dust grains. One belt sits approximately 5.9 AU away from the central binary, or about the distance from the sun to Jupiter, and is likely made up of asteroids and comets. The other belt sits at 1.5 to 2 AU, comparable to the area where Mars and the asteroid belt sit, and consists of fine dust grains

Source: NASA/CalTech - Spitzer- Newsroom

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